This invention relates to a low level freight car for carrying trailers and containers and particularly to a low level freight car adapted for intermodal use.
The prior art has provided a variety of low level freight cars adapted to carry trailers, etc. in "piggy back" fashion. In order to clear bridges and tunnels, various types of low level flat bed and well cars have been designed. Certain of these designs, such as shown in the Budd U.S. Pat. No. 4,456,413, employ a pair of spaced side sill assemblies which accommodate buff and draft forces while also supporting a floor structure which carries vertical loadings applied by the trailer or container. The underframe structure in the lighter designs may be subject to excessive deflection under load, while in the low-deflection designs, excessive tare weight due to the heavy sill structure needed may pose a problem. Hence there is a need for an improved low-level, low deflection, relatively low-tare weight freight car for transporting trailers, containers and the like. There is also a need to provide cars of this variety which are capable of intermodal use, the cars being articulated together by special connectors, known as such, with adjacent ends of the cars sharing a single truck to make full use of axle loading capacity and thereby keeping tare weight down.